Shares of Boeing fell nearly 2 percent Monday after reports that the company is considering not bidding in the next round for the Pentagon’s $35 billion airborne refueling tanker contract.

Aviation Week reports that the company is “strongly considering” not submitting a bid for the Air Force tanker after the Pentagon issued new guidelines last week for the plane. The report cited unnamed sources familiar with Boeing’s internal strategy, but the company did not comment.

Boeing’s Capitol Hill supporters have complained that the new rules favor Northrop Grumman’s larger plane and give Boeing little time to make any changes to its original proposal.

Boeing lost the first round of bidding to rival Northrop Grumman and Airbus parent EADS earlier this year, but the Government Accountability Office later ruled that the Air Force had committed several errors in awarding the contract. The Pentagon decided to reopen the bidding and hopes to award a new contract by the end of the year.

The new request for proposal said the Pentagon will give “additional value” to a plane that can carry more fuel than is required. Boeing’s supporters say that unfairly favors Northrop’s larger plane. (AP)